Problem: Before the previous stop there were 37 people riding on a train. 19 people ended up getting off at the stop. How many people are riding the train now?
Answer: The number riding the train now is the difference between the number who were riding and the number who got off at the previous stop. The difference is $37 - 19$ people on the train. $37 - 19 = 18$ people are on the train.